Since the 1950s it is known that sweat secreted by the apocrine glands is odourless and the undesirable smell of sweat only develops through bacterial action. Accordingly, it was concluded that sweat contains malodour precursors and malodourants are released through the enzymatic action of bacteria on said precursors.
Body malodour, including in particular axilla malodour, is due to three main classes of compounds: Sulfanylalcohols, unsaturated or hydroxylated acids, and steroids. The methods described herein are useful to identify inhibitors that prevent the formation of sulfanylalcohols.
Applicant previously identified the malodour precursor for the unsaturated or hydroxylated acids, and the aminoacylase enzyme (“AMRE”) forming them (EP 1258531). The AMRE enzyme can be used to screen for inhibitors of the malodour forming enzymes and thereby to identify compounds to prevent or reduce body malodour.
For the release of sulfanylalcohols, applicant identified a cystathionine-β-lyase from Corynebacterium sp. Ax20 and a precursor compound (A. Natsch et al., Chemistry & Biodiversity 2004, 1058).
Starkenmann et al. postulated a different β-lyase from Staphylococcus haemolyticus releasing sulfanylalcohols from a different precursor, namely the precursor of formula FIII (WO2006079934).

While Staphylococcus bacteriae are generally not believed to be involved in malodour formation to a major extent, the compound of FIII (in the examples: “cys-gly-conjugate”) seems to contribute to body malodour nonetheless.
The sequence SEQ ID NO: 3, and SEQ ID NO:4 as its hypothetical gene product, were previously published in a sequence database, but the protein function, catalytic activity and its involvement in malodour generation were not known.
Applicant has now surprisingly identified a third type of enzyme (peptidases including but not limited to SEQ ID NO:2 and SEQ ID NO:4) that releases a precursor II from a precursor I (for example, without limitation, compound of FIII) or alternatively, various other substrates described herein below, and together with the action of the previously identified cystationin-β-lyase finally forms a sulfanyl alcohol malodourant (compare FIG. 1).
Both the novel type of peptidase and the β-lyase previously described by applicants occur in Corynebacteria. Without wishing to be bound by theory, it is generally accepted that highly unpleasant malodour is released from fresh sweat mainly by Corynebacteria. 
Applicant showed that no single fraction of C. sp. Ax20 extract was able to release malodourant from the precursor I, in particular, without limitation, compound FIII. This demonstrates that there is no single enzyme present in C. sp. extracts that can cleave precursor I (compare examples herein-below, in particular example 11). Further applicant showed that two enzymes are mediating the cleavage of precursor I, in particular, without limitation, compound of FIII: first a peptidase (for example, without limitation, SEQ ID NO: 2 or NO:4) cleaving the dipeptide between the gly and the cys residue, and then a β-Lyase subsequently releasing the malodourant from the cys-conjugate (FIV) formed by the peptidase (compare examples herein-below, in particular example 12).

The identified type of enzyme is useful as an alternative screening target to identify inhibitors of malodour formation by sulfanyl alcohol malodourants.
Precursor I (physiologically relevant substrates) has the general formula FII
    wherein R1 is selected from a group of alkane residues consisting of methyl, ethyl, propyl, butyl, pentyl, and hexyl    and wherein R2 and R3 are independently selected from the group consisting of H and methyl.
Accordingly, the sulfanylalkanol malodourant has the general formula FV
    wherein R1 is selected from a group of alkane residues consisting of methyl, ethyl, propyl, butyl, pentyl, and hexyl    and wherein R2 and R3 are independently selected from the group consisting of H and methyl.
The peptidases will also react non-physiological substrates of formula FI as detailed herein-below under the section “substrates of peptidase”, that are useful for screening purposes.
The type of peptidase enzyme is particularly interesting since, without wishing to be bound by theory, not only does it occur in the most relevant genus of bacteria, but this type of peptidase enzymes seem to perform the rate limiting step in the malodour forming enzymatic reactions, and the identified inhibitors can therefore expected to be particularly effective.
Still further, again without wishing to be bound by theory, both embodiments of peptidase (SEQ ID NO: 2 and SEQ ID NO: 4) belong to the same class of enzymes (metallopeptidases) as the previously identified AMRE enzyme that forms malodourous unsaturated or hydroxylated acids, and screening with the peptidase enzymes (including, without limitation, enzymes of SEQ ID 2 and SEQ ID 4) may result in finding inhibitors also active against the metallopeptidases involved in the formation of malodourous unsaturated or hydroxylated acids and therefore effective to reduce formation of malodourants of both classes at the same time.